This is very interesting as I have never heard of magnesium irritating the heart lining, You always thought well magnesium helps muscles and it can also help the heart. But never did I think it would actually do something to the lining. I do however tend to think that many supplements/vitamins that are not well purified and have extra dusty fillers in them(i'm thinking of a few NOW foods ones) These ones in particular seem to cause allergic reactions to me in particular, which is why I stay away from them. Most of the thorne research ones are fine with me, just certain ones I know aren't of good quality.